Packaging materials with enhanced thermal-insulating performance

ABSTRACT

A thermo-insulating packaging material including a paper-based substrate layer, a paper-based top layer and a thermal-insulating composition positioned between the paper-based substrate layer and the paper-based top layer, the thermal-insulating composition including a filler, an organic binder and a plasticizer.

PRIORITY

This application is a continuation of U.S. Ser. No. 13/080,064 filed onApr. 5, 2011 (pending), which is a continuation of PCT/US2010/033653(national phase) filed on May 5, 2010, which claims priority from U.S.Ser. No. 61/175,569 (expired) filed on May 5, 2009 and U.S. Ser. No.61/287,990 filed on Dec. 18, 2009. The entire contents of all fourpriority applications are incorporated herein by reference.

FIELD

This application relates to packaging materials and, more particularly,to thermal-insulating packaging materials, such as cups and containers.

BACKGROUND

Paperboard is a low-cost material that is ubiquitous in the field ofpackaging generally. Its strength and thermal insulation properties arehowever limited, and laminates with other materials have been developedand are widely used. For example, U.S. Pat. Nos. 7,192,640 and 5,091,261disclose paperboard/polymer laminates for forming blister packs. Thesepatents do not disclose the use of such laminates for making paper cupsor other food or beverage containers. U.S. Pat. No. 6,811,843 describesa cup formed from a laminate including an insulating layer and a paperstock layer. The insulating layer is heat-laminated foam formed fromhigh density polyethylene, low density polyethylene, linear low densitypolyethylene, or oriented polypropylene. U.S. Pat. No. 6,277,454discloses a single-walled container for storing hot or cold liquids,comprising an inner layer of paperboard laminated to an outer layer ofsyntactic foam. Void-containing particles in the foam improve thethermal insulation. The syntactic foam outer layer contains voidstructure and a regular pattern, such as stripes or dots, to improve thethermal insulation.

A single-walled container is known for its limitation of strength, andits vulnerability to damage of the exposed pattern of foam. Since suchcontainers are intended to hold scalding hot liquids, thesedisadvantages can give rise to product liability issues. A double-walledlaminate container is sturdier, but the doubled laminated structure haspoor flexibility. Therefore, it is relatively difficult in forming thedoubled laminated structure into a container shape using the standardcup-making machines.

Additionally, there has been increased environmental concern forbiodegradability and recycling of packaging materials. Synthetic foamsand thermosetting plastics are neither biodegradable nor recyclable, andin many cases they produce toxic breakdown products when incinerated.Therefore, the known thermally insulating packaging materials andcontainers made of paperboard/polymer laminates presents environmentalconcerns.

Accordingly, there is a need for the biodegradable packaging materialwith enhanced thermal-insulating performance and strength that allowsfor its production using the existing papermaking process and for itsformation into the packaging containers using the existing convertingprocess, such that an improved cost per package may be achieved and thepackaging containers may be formed, filled and sealed at economicallyhigh speeds using conventional packaging machine temperatures, pressuresand dwell times.

SUMMARY

A packaging material with enhanced thermal-insulating performance isdisclosed that includes a paper-based substrate and a thermal-insulatinglayer positioned on at least one surface of the substrate. Thethermal-insulating layer contains void structure and is derived from afluid thermal-insulating composition comprising: 20% to 70% weight offiller; 15% to 70% weight of organic binder; 0.5% to 10 weight ofplasticizer; and 10% to 15% weight of moisture, based on the totalthermo-insulating composition weight. When desired, the disclosedpackaging material may further include a paper-based top layer such thatthe thermal-insulating layer is positioned between the paper-basedsubstrate and the paper-based top layer. The disclosed packagingmaterial may be used in the formation of thermo-insulating containerssuch as food bowls and beverage cups, as well as the sleeve componentsto impart thermo-insulating performance to packaging containers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows one embodiment of the disclosed production process of thepackaging materials with enhanced thermal-insulating performance;

FIG. 2 a shows one embodiment of the disclosed production processwherein the thermal-insulating composition is spray-applied onto thepaper-based substrate as essentially continuous sinuous strands;

FIG. 2 b shows one embodiment of the disclosed production processwherein the thermal-insulating composition is spray-applied onto thepaper-based substrate in a random spray pattern;

FIG. 3 shows one embodiment of the present disclosure wherein thethermal-insulating packaging material is used in the formation of cup;and

FIG. 4 shows one embodiment of the present disclosure wherein thedisclosed thermal-insulating packaging material is used in the formationof sleeve for a container, demonstrating the cross-section of thecontainer and the thermal-insulating sleeve.

DETAILED DESCRIPTION

While the disclosure has been described with reference to exemplaryembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the disclosure. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the disclosure without departing fromthe essential scope thereof.

The packaging material of the present disclosure includes:

(A) a paper-based substrate; and

(B) a thermal-insulating layer positioned on at least one surface of thesubstrate, the thermal-insulating layer containing void structure andbeing derived from a fluid thermal-insulating composition comprisingbased on total weight of the composition:

-   -   (a) filler in an amount of 20% to 70% weight;    -   (b) organic binder in an amount of 15% to 70% weight;    -   (c) plasticizer in an amount of 0.5% to 10 weight; and    -   (d) moisture in an amount of 10% to 15% weight.

In one embodiment of the present disclosure, the filler used in thefluid thermal-insulating composition comprises, based on total weight ofthe filler:

-   -   (i) inorganic filler in an amount of 0% to 90% weight; and    -   (ii) organic filler in an amount of 10% to 100% weight.

In one embodiment of the present disclosure, the filler used in thefluid thermal-insulating composition comprises, based on total weight ofthe filler:

-   -   (i) inorganic filler in an amount of 40% to 90% weight; and    -   (ii) organic filler in an amount of 10% to 60% weight.

The disclosed packaging material may be produced by a process includingsteps of:

-   -   (I) providing a paper-based substrate having a first and a        second surfaces;    -   (II) applying a thermal-insulating layer onto the first surface        of the paper-based substrate to provide a coated structure, the        thermally insulating layer containing void structure and being        derived from the aforementioned fluid thermal-insulating        composition; and    -   (III) drying the coated structure to reduce a water content of        the thermal-insulating layer to a range of 10% to 15% weight,        based on total weight of the thermal-insulating layer.

In one embodiment, the disclosed process of producing the presentthermal-insulating packaging material may further include a step ofapplying a paper-based top layer onto the dried, coated structure ofstep (III) such that the thermal-insulating layer is positioned betweenthe paper-based substrate and the paper-based top layer. For thisembodiment, the disclosed thermal-insulating packaging materialincludes:

-   -   (A) a paper-based substrate having a first and a second        surfaces;    -   (B) a paper-based top layer; and    -   (C) a thermal-insulating layer positioned between the first        surface of the paper-based substrate and the paper-based top        layer, wherein the thermal-insulating layer contains void        structure and is derived from the aforementioned        thermal-insulating composition.

When desired, the process of producing the present thermal-insulatingpackaging material may further include a step of applying a moisturebarrier composition to the other surface of the paper-based substratethat is opposite to the surface coated with the thermal-insulatinglayer. For this embodiment, the disclosed thermal-insulating packagingmaterial includes:

-   -   (A) a paper-based substrate having a first and a second        surfaces;    -   (B) a paper-based top layer;    -   (C) a thermal-insulating layer positioned between the first        surface of the paper-based substrate and the paper-based top        layer, wherein the thermal-insulating layer contains void        structure and is derived from the aforementioned        thermal-insulating composition; and    -   (D) a moisture barrier layer positioned on the second surface of        the paper-based substrate.

In one embodiment, the thermal-insulating layer may be placed betweenthe paper-based substrate and the paper-based top layer to provide asandwich structure such that the thickness of the final assemblystructure is 20% to 100% greater than the combined thickness of thepaper-based substrate and the paper-based top layer. In this embodiment,the thermal-insulating layer acts as a spacer and provides forseparation of the two paper-based layers. It is believed that thedisclosed thermal-insulating layer is able to provide this spacingproperty due to its fluid pseudoplastic characteristics combined withits unique component properties.

Several application techniques may be used to deposit thethermal-insulating composition onto the paper-based substrate. Examplesinclude, but are not limited to, rod coating, blade coating, curtaincoating, spray coating, and extrusion.

The thermal-insulating composition may be applied onto the paper-basedsubstrate in a form of coalesced droplets, longitudinally-extendingsinuous strands, or combinations thereof. When the thermal-insulatingcomposition is applied in a form of strands, the strands may have athickness range of 0.05 mm to 0.5 mm.

In one embodiment, the thermal-insulating composition may be appliedonto the paper-based substrate using a standard spray depositionapparatus that is low cost and resistant to mechanical damage.

In one embodiment, the thermal-insulating composition may be appliedonto the paper-based substrate in a form of foam incorporating anemulsion polymer binder. Additionally, the foam may comprisemechanically whipped latex.

In one embodiment, the fluid thermal-insulating composition has apseudoplasticity index in a range 0.3 to 0.5.

In one embodiment, the fluid thermal-insulating composition may have alow shear viscosity in a range of 2,000 to 50,000 centipoises and a highshear viscosity in a range of 100 to 5,000 centipoises.

In one embodiment, the thermal-insulating layer of the presentdisclosure may be tailored to hold pressures in the range of 0.1 kgf/cm²to 1.0 kgf/cm² (10 Kpa to 100 Kpa).

In one embodiment, the thermal-insulating layer may be applied on thesurface of the paper-based substrate, such as via spraying application,to create a textured surface. Two-ply paperboard may be used aspaper-based substrate, paper-based top layer, or both.

The thermal-insulating composition may be selectively applied onto thesurface of paper-based substrate such that the resultingthermal-insulating layer may be selectively patterned and imparted ontothe paper-based substrate. For example, the thermal-insulating layer maybe selectively applied such that the container formed from the disclosedthermal-insulating packaging material has enhanced thermal-insulatingperformance at the selected portion. Accordingly, the need for asecondary thermal insulator to be wrapped around the container may beeliminated. This aspect of the disclosure is particularly useful whenthe disclosed thermal-insulating packaging material is used for hotbeverage applications.

A variety of drying techniques may be used in the drying step (III) ofthe disclose method. Examples of such drying techniques include, but arenot limited, to heated air, hot plates, infrared heating, andcombinations thereof. When appropriate, the thermal-insulatingcomposition may include a humectant to assist in maintaining themoisture content at the selected level.

In one embodiment of the present disclosure, the thermal-insulatingpackaging material may be used for the formation of single-layer cups.

In one embodiment of the present disclosure, the thermal-insulatingpackaging material may be used for the formation of two-layer cups. Thedisclosed thermal-insulating packaging material may be applied in atwo-layer cup machine as a second layer on a cup made from conventionalpaperboard substrate. Several commercially available cup machines may beused. Examples are the cup machines from Paper Machinery Corporation ofWisconsin, USA; Hörauf America, LLC of Pennsylvania, USA; and thosedisclosed in U.S. Pat. No. 5,324,249.

FIG. 1 shows one embodiment of the disclosed production process. Upperand lower feed rolls 1 and 2 supply upper and lower paper-based webs P1and P2 to a flatbed laminating machine (such as the Glenro model HPHmachine available from Glenro Inc., New Jersey, USA) and thence to atake-up roll 4. The fluid thermal-insulating composition is stored incontrolled hopper 4, fed to the applicator 3, and then applied onto asurface of the paper-based substrate web P2. For example, the applicator3 may be a fiber spray applicator such as a UFD High Speed—Auto AdhesiveApplicator available from ITW Dynatech, Tennessee, USA. The appliedsubstrate web P2 is then dried, such as by the means of infrared heater5, to provide a web of paper-based substrate P2 with a thermallyinsulating layer S on its surface. The coated paper-based substrate isthen combined with the paper-based top layer web P1 that is guided overguide rolls 6 and 7. The resulting assembly is subjected to the nip ofguide roll 7 and an underlying conveyor belt B2 of the laminator L.Downstream of guide roll 7, compression of the resulting laminate ismaintained by an upper conveyor belt B1 of the laminator which opposesthe upper run of conveyor belt B2. Both these conveyor belts run onguide rolls r and apply heat and pressure from electric heating platesH. The thermal-insulating layer S may be controllably dried to amoisture content of 10% to 15% weight of the total layer weight.Finally, the resulting thermal-insulating laminate 10 is received bytake-up roll 4. When desired, the porosity of the paper-based substrate,such as paperboard, may be selected to be in the range of 20 to 150Gurley units to provide a path for steam to escape during the dryingprocess in the laminator L.

In one embodiment, the thermal-insulating composition may be formulatedsuch that it has strong pseudoplastic characteristics with a low shearBrookfield viscosity of 2,000 to 50,000 cps to hold the gap between thepaper-based webs P1 and P2.

In one embodiment, the thermal-insulating composition may have aviscosity of greater than 10,000 cps.

Example of the organic binders suitable for use in the disclosedthermal-insulating composition may include, but are not limited to,styrene-butadiene polymer, an acrylic-styrene butadiene-latex binder,starch, polyvinyl alcohol, polyvinyl acetate, and combinations thereof.In one embodiment, the binder may include a Stein Hall reaction mixture,namely a mixture of sodium hydroxide solution, raw pearl (i.e.,ungelatinized) starch and borax. Upon heating in the laminator L asshown in FIG. 1, the starch gelatinizes and absorbs water, andsubsequently creates a rapid green bond between the paper-based webs P1and P2. Furthermore, the remaining unreacted raw starch particles mayact as mechanical spacers keeping the paper-based webs apart.

In one embodiment, the thermal-insulating composition comprises no morethan 20% weight of starch binder based on total composition weight. Inone embodiment, the starch binder may include 10% to 50% by weight ofgelatinized starch and 50% to 90% by weight of ungelatinized starch. Inother embodiment, the starch binder may include 0% to 70% by weight ofgelatinized starch and 30% to 100% by weight of ungelatinized starch. Inother embodiment, the starch binder may include 50% to 100% by weight ofgelatinized starch and 0% to 50% by weight of ungelatinized starch.

In yet another embodiment, the thermal-insulating composition comprisesmore than 20% weight of starch binder based on total composition weight,wherein the starch binder may include 10% to 50% by weight ofgelatinized starch and 50% to 90% by weight of ungelatinized starch.

Suitable fillers for use in the disclosed thermal-insulating compositionmay include organic filler, inorganic filler, or combinations thereof.Examples of such fillers include, but are not limited to, cellulosicfibers, wood flour, pearl starch, calcium carbonate, sawdust, gypsum,plaster, clay, corn seed skin, gluten feed, and combinations thereof.Gluten feed is a corn byproduct that may impart the disclosedthermal-insulating packaging material with enhanced tear resistance,compression and edge strength.

In one embodiment, the thermal-insulating composition may includecellulosic fibers, wood flour, or combinations thereof, in an amount of2% to 10% weight based on the total composition weight to impart anenhanced tear resistance to the final packaging material.

In one embodiment, the thermal-insulating composition may includecellulosic fibers as organic filler in a range of 2% to less than 50% byweight based on the total composition weight. In one embodiment, thecellulosic solids may have a particle size of more than 100 microns.Examples of suitable cellulosic solids include, but are not limited to,cellulosic fibers, wood flour, wood dust, gluten feed, and combinationsthereof. When desired, the cellulosic fibers may have a length of nogreater than 2 mm and an aspect ratio of no greater than 25:1.

In one embodiment, the thermal-insulating composition may include cornfibers in the range of 0.5% to less than 1% by weight based on the totalcomposition weight.

In one embodiment, the filler component of the thermal-insulatingcomposition may comprise insulating particles selected from the groupconsisting of ceramic air-containing particles, pearlite particles, andcombinations thereof.

In one embodiment, the thermal-insulating composition may includemechanically-induced foam comprising an emulsion polymer binder and afoam stabilizer. Examples of suitable emulsion polymer binders include,but are not limited to, styrene-butadiene latex, acrylic-SRB-latex,starch, and combinations thereof. Additionally, mechanically whippedlatex may be used as the foam component in the disclosedthermal-insulating composition. To reduce the cost, thethermal-insulating composition may further include filler materials.Examples of suitable fillers include, but are not limited to, cellulosicinsulation such as those available from Cell-Pak LLC and Nu-WoolCompany, Inc.; wood flour; sawdust cellulose pulp; rayon fiber;synthetic fibers; and combinations thereof. When desired, the binder andfillers may be whipped together.

In one embodiment, the disclosed thermal-insulating composition furtherincludes borax.

In one embodiment, the disclosed thermal-insulating composition mayinclude sodium silicate filler in an amount of 1% to 15% weight based onthe total composition weight.

In one embodiment, the disclosed thermal-insulating composition includesungelatinized starch organic binder and sodium silicate filler.

In one embodiment, the disclosed thermal-insulating compositioncomprises, based on the total composition weight: ungelatinized starchbinder in an amount of 5% to 32% weight and sodium silicate filler in anamount of 1% to 15% weight. Both these materials are natural materialswhich do not cause environmental problems when disposed of. Importantly,sodium silicate in solution may undergo a dramatic increase in viscosityand hence resilience when the water content is reduced. Ungelatinizedstarch absorbs water strongly when heated and hence the combination ofmaterials is synergistic, in that they may be deposited easily inaqueous solution (low viscosity) and on heating set to a high-viscosityresilient state in which the thermally insulating material may be passedthrough a laminating machine without undue compression. In addition toits outstanding adhesive properties, sodium silicate has the advantageof a very strong dependence of viscosity on concentration. Therefore, itbehaves synergistically with ungelatinized starch: as the starch isheated in the laminator L, it absorbs water and hence raises theviscosity of the sodium silicate-containing solution very substantially,thereby maintaining the spacing between the upper and lower paperboardwebs.

To further improve the thermal insulation properties, the disclosedthermal-insulating layer may include void-containing particles. Examplesof suitable void-containing particles include, but are not limited to,pearlite, hollow ceramic particles, kenaf core, and combinationsthereof.

TABLE 1 shows examples of the disclosed thermal-insulating compositionsthat may be applied onto the paper-based substrate web P2 using thefiber spray applicator 3.

TABLE 1 EXAMPLE NO. (Parts by Weight) Material No 1 No 2 No 3 No 4Component cellulosic insulation 2 2 2 2 FILLER (recycled newsprint)calcium carbonate 100 100 100 100 FILLER clay @40% solids 150 150 150150 FILLER latex SBR @40% solids 75 75 75 75 BINDER pearl starch 100 10100 100 BINDER PVOH 0 5 10 10 BINDER sorbitol 5 — — — PLASTICIZER Emtalemulsified fatty 5 5 — — PLASTICIZER acids @40% solids glycerine — — 5 5PLASTICIZER Safoam FPN3 1 1 1 1 FOAMING AGENT sawdust 3 3 3 3 FILLERTriton 100 0.5 0.5 0.5 SURFACTANT pearlite — — 1 3 FILLER sodiumsilicate 2 2 — — BINDER

TABLE 2 shows yet more examples of the thermal-insulating compositionssuitable for use in the present disclosure.

TABLE 2 Components in the % Weight based on total Thermally InsulatingComposition weight of the Composition Cellulosic insulation (recyclednewsprint)  0-5% Calcium carbonate 5-40% Latex SBR @40% solids 5-30%Pearl starch 5-32% PVOH 5-15% Sorbitol 5-10% Emtal emulsified fattyacids @40% solids 5-11% Glycerine 5-12% Safoam FPN3  1-2% Sawdust 5-20%Triton 100 0.1-2%  Pearlite 0-40% Sodium silicate 0-15%

In one embodiment, the thermal-insulating layer S may have a substantialthickness, such as in a range of 0.2 mm to 5 mm. To reduce the energyrequired in drying the thermally insulating layer, the solids content ofthe thermal-insulating composition may be in a range of 50% to 70%weight based on the total composition weights. To further reduce thedrying energy, the first thermal-insulating composition may be depositedas a first layer on paper-based substrate web P1 and then dried to asolids content of 60% to 90%. Then, a layer of the secondthermal-insulating composition may be deposited on the first layer,wherein the second thermal-insulating composition may have a solidscontent of 30% and 50% and may include tackifier. Examples of suitabletackifiers may include, but are not limited to, rosin, rosin ester,acrylics, aliphatic resins, aromatic resins, or combinations thereof.The second layer of the thermal-insulating composition may be relativelythin, with a weight per unit length of 2% to 10% compared to that of thefirst layer of the thermal-insulating composition.

Referring to one embodiment of the disclosed process as shown in FIG. 2a, the fiber spray applicator 3 is equipped with a nozzle N arranged todeposit an essentially continuous sinuous strand St of thethermal-insulating composition in an omega pattern on the paper-basedweb P2, which may be continuously transported to the right as shown bythe arrow. The pattern shape may be controlled by the pseudo-plasticityof the disclosed thermal-insulating composition. The pseudoplasticityindex of the thermal-insulating composition may be in a range of 0.3 to0.5. In one embodiment, the pseudoplasticity index of the disclosedthermally insulating composition may be in a range of 0.4 to 0.45. Apseudoplastic fluid has the property that at low shear rates, theviscosity is relatively high and at high shear rates, the viscosity isrelatively low. The pseudoplasticity index N is a measure of thisdeviation from shear rate-independent viscosity and may be calculatedfrom the following equation:T=K×G ^(N)where K is a coefficient which is dependent on the material type, T isshear stress, and G is shear rate.

Materials which impart pseudoplasticity are known to one skilled in thearts. Examples of such materials are latex and low solids starchsolutions; whereas, certain proteins make the formulation lesspseudoplastic. Therefore, one skilled in the arts would recognize andmay tailor the disclosed pseudoplastic thermal-insulating compositionsuch that it is deposited easily onto the paper-based substrate due toits high shear rate (for example, via its flow through a nozzle), andyet it is stable upon deposition because the compressive forces itexperiences in a laminating machine are low shear-rate. Accordingly, thelayer of thermal-insulating composition, once deposited onto thepaper-based substrate, is dimensionally stable and may be passed througha laminating machine without undue compression. This arrangement couldminimize material cost and ensure that voids are formed between theloops of bonding thermally insulating layer in the finished product. Thethickness of the strand St may be set in a range of 0.05 mm to 5 mm.

FIG. 2 b shows one embodiment of the disclosed process, whereindiscontinuous strands St and coalesced droplets of the disclosedthermal-insulating composition may be deposited in a random pattern.This may be achieved by adjusting the discharge from the nozzles, thespeed of the moving webs, as well as the pseudoplasticity, pressure andthe surface tension of the thermal-insulating composition. In oneembodiment, approximately 20% to 60% of the total surface of thepaper-based substrate P2 may be covered with the thermal-insulatingcomposition. The topograhy of the thermal-insulating layer may includesome undulations, depending on the ingredient, rheology, and surfacetension of the thermally insulating composition. In one embodiment, thethermal-insulating composition may have a surface tension in a range of10 dyne/cm to 40 dyne/cm.

The disclosed packaging material has enhanced strength and stiffness, aswell as improved thermal insulation. They are suitable for manypackaging applications and may be formed in various packaging containerssuch as food or beverage containers. The disclosed packaging containershave enhanced strength, thermal insulation, and resistance to damage.Additionally, the disclosed packaging material and the packagingcontainers thereof have improved biodegradability.

The disclosed packaging material may be used for the formation of thedouble-walled thermal-insulating containers. The disclosed packagingmaterial has a significantly improved flexibility that allows for itsformation into the container shapes using the standard convertingmachinery, such as a standard paper cup-making machine.

When desired, the disclosed packaging material may be used as a sleevefor packaging containers to provide the thermal-insulating performance.

In one embodiment of the present disclosure, the disclosedthermal-insulating material 10 is formed into a cup C as shown in FIG.3, using standard cup making or sleeve-making apparatus.

In one embodiment of the disclosed process, the thermal-insulatingcomposition may be deposited onto the paper-based substrate on a movingnon-stick conveyor, without the paperboard feed systems as shown inFIG. 1. The produced thermal-insulating material may then be formed intothe cup or sleeve using standard apparatus.

In one embodiment, the thermal-insulating layer S of the thermallyinsulating material may then be dried further to a moisture contentbelow 10% to 15% weight to impart sufficient flexible, allowing thematerial to be processed in a cup making machine.

In one embodiment of the present disclosure, the disclosedthermal-insulating packaging material may be used in the formation ofsleeve for a container, and the cross-section of the container and thethermal-insulating sleeve is as shown in FIG. 4. The disclosedthermal-insulating material 10 may be produced from the process of FIG.2 b. The thermal-insulating material 10 comprises: the paper-basedlayers P1 and P2; the thermal-insulating layer t sandwiched between thetwo paper-based layers P1 and P2; and two moisture barrier layers MB,each MB layer being positioned on the other surface of the paper-basedlayers P1 and P2. The thermal-insulating layer t includes strands St andcoalesced droplets CD of the thermally insulating composition, alongwith voids V. In FIG. 4, the disclosed thermal-insulating material 10 isused as a sleeve that wraps around a cup wall 11. Several knownpackaging materials may be used for the formation of the cup 11.Examples of these known packaging materials for cup formation include,but are not limited to, polystyrene foam, paper-based materials, plasticpolymer, and combinations thereof. In one embodiment, the thickness ofthe thermal-insulating layer S may be in a range of 0.05 mm to 0.5 mm.

It is understood that from the present disclosure, one skilled in thearts may readily modify the production process; the compositions of thethermal-insulating layer; and the structure of the thermal-insulatingpackaging materials to facilitate the selected end-use applications. Forexample, the thermal-insulating composition may include the byproductsof corn, such as corn gluten feed, to impart a significant improvementof the strength and stiffness to the resulting thermal-insulatingpackaging material and the packages produced therefrom.

Although various aspects of the disclosed packaging materials withenhanced thermal-insulating performance have been shown and described,modifications may occur to those skilled in the art upon reading thespecification. The present application includes such modifications andis limited only by the scope of the claims.

What is claimed is:
 1. A thermo-insulating packaging materialcomprising: (A) a paper-based substrate layer; (B) a paper-based toplayer; and (C) a thermal-insulating composition positioned between thepaper-based substrate layer and the paper-based top layer, thethermal-insulating composition comprising a filler, an organic binderand a plasticizer.
 2. The material of claim 1 further comprising amoisture barrier layer, and wherein the moisture barrier layer ispositioned on at least one of the paper-based substrate layer and thepaper-based top layer.
 3. The material of claim 1 wherein the fillercomprises, based on total weight of the filler: (i) inorganic filler inan amount of 0% to 90% by weight; and (ii) organic filler in an amountof 10% to 100% by weight.
 4. The material of claim 1 wherein thethermal-insulating composition is positioned on at least one of thepaper-based substrate layer and the paper-based top layer in a form ofcoalesced droplets, longitudinally-extending sinuous strands, orcombinations thereof.
 5. The material of claim 1 wherein thethermal-insulating composition comprises a starch binder.
 6. Thematerial of claim 1 wherein the thermal-insulating composition furthercomprises borax.
 7. The material of claim 1 wherein thethermal-insulating composition comprises ungelatinized starch and sodiumsilicate.
 8. The material of claim 1 wherein the thermal-insulatingcomposition comprises corn fibers as the filler in an amount of 0.5% to1% by weight based on total weight of the composition.
 9. The materialof claim 1 wherein the filler comprises insulating particles selectedfrom the group consisting of ceramic air-containing particles, pearliteparticles, and combinations thereof.
 10. The material of claim 1 whereinthe organic binder comprises a member selected from the group consistingof styrene-butadiene polymer, an acrylic-styrene butadiene polymer,starch, polyvinyl alcohol, polyvinyl acetate, and combinations thereof.11. The material of claim 1 characterized by a thickness of thethermal-insulating composition in a range of 0.05 mm to 5 mm.
 12. Thematerial of claim 1 wherein the thermal-insulating composition isapplied to at least one of said paper-based substrate layer and saidpaper-based top layer as a fluid, and wherein the fluid has apseudoplasticity index in a range of 0.3 to 0.5.
 13. The material ofclaim 1 wherein the thermal-insulating composition is applied to atleast one of said paper-based substrate layer and said paper-based toplayer as a fluid, and wherein the fluid has a low shear viscosity in arange of 2,000 to 50,000 cps, and a high shear viscosity in a range of100 to 5,000 cps.
 14. The material of claim 1 characterized by aporosity of the paper-based substrate layer in a range 20 to 150 Gurleyunits.
 15. The material of claim 1 characterized by a porosity of thepaper-based top layer in a range 20 to 150 Gurley units.
 16. Thematerial of claim 1 wherein the filler comprises at least 15 percent byweight of the thermal-insulating composition.
 17. The material of claim16 wherein the organic binder comprises 15% to 70% by weight of thethermal-insulating composition.
 18. The material of claim 1 wherein thethermal-insulating composition comprises cellulosic solids as the fillerin an amount of 2% to 50% by weight based on total weight of thecomposition.
 19. The material of claim 18 wherein the cellulosic solidshave an average particle size of at least 100 microns.
 20. The materialof claim 18 wherein the cellulosic solids include a member selected fromthe group consisting of cellulosic fibers, wood flour, wood dust, glutenfeed, and combinations thereof.